I wouldn't recommend using gsc to set prestige (because it doesn't stick) but you can try something like this
Prestige(num)
{
self iPrintln("Prestige Set To " + num);
self.pres["prestige"] = num;
self setdstat("playerstatslist", "plevel", "StatValue", num);
rank = getrank();
self setrank(rank,num);
}
self add_option("SubMenu2", "Prestige 1", :

restige, 1);
self add_option("SubMenu2", "Prestige 2", :

restige, 2);
self add_option("SubMenu2", "Prestige 3", :

restige, 3);
etc